IRSN has begun preliminary simulations of the Fukushima Daiichi accident using its ASTEC software, designed to simulate core meltdown accidents. These simulations aim for an understanding of the various phases of the accident in terms of hydrogen production, fuel damage, fission product releases and corium progression. The data will also be useful for safety assessments of French reactors.
Given the lack of any direct detailed observation of damage to the reactor cores at the Japanese plant, the only way to reconstruct the various phases of the accident is with simulation tools that use currently available data on core meltdown accidents. After collecting data relating to plant configuration and the accident sequence, the ASTEC software program developed jointly by IRSN and GRS was used in conjunction with a simplified model of the reactor. Preliminary results for unit 2 of the Fukushima Daiichi plant were found to be consistent with pressure changes recorded by TEPCO, the plant operator.
They also provided data on hydrogen production and core damage that are consistent with data collected by other teams. Based on these initial results, development work specific to boiling water reactors will continue to refine the simulation capabilities of ASTEC (initially developed for pressurized water reactors) and make it a standard reference for severe accident simulations.
For more information:
The ASTEC Software Package : Complete simulation of severe accidents